The present invention relates to a portable electronic device, specifically to a so-called IC card, which is used in a banking system or shopping system, and which incorporate an IC (Integrated Circuit) chip having a nonvolatile data memory and a control element, e.g., a CPU (Central Processing Unit).
In recent years, an IC card incorporating an IC chip having a nonvolatile data memory and a control element (e.g., a CPU) has been proposed. Data stored in the memory of this IC card is managed by a control element incorporated therein or by an IC card reader/writer connected to the IC card.
A banking system or a shopping system has been proposed as a practical application for the IC card. In this application, the validity of data must be checked. When data is written in the memory, it can be read out in order to check if it has been properly written. However, when data written in the memory is read out, there is no means for checking if it has been properly read out.